Microprobes are used today in radiobiology to investigate the effects of ionising radiation on biological cells and tissue. In contrast to broad field irradiation, they provide the possibility to deliver a defined number of ions to selected areas in single cells. Therefore the dose and even the dose distribution can be controlled very precisely. This capability is particularly used for the investigation of low dose effects, where each cell is traversed by exactly one particle. With that, the estimation about the radiation risk of environmental exposures caused by alpha-particle emitting isotopes shall be improved. The aimed irradiation is also appropriate for studying the so-called "bystander effect", where unirradiated cells respond to signals transmitted by irradiated neighbours. In this work the heavy-ion-microprobe of GSI was modified to enable the irradiation of single cells with a defined number of particles. To separate the beamtube from the area under ambient pressure where the cells are, a vacuum-window had to be developed that can be penetrated by the ions with minimal scattering. The secondary electrons emitted by this vacuum-window when an ion passes are used for the hit detection. Additionally a cell-dish had to be developed in which the cells can be cultured, i.e. they have to attach to a thin bottom-foil through which they can be irradiated. This dish is mounted in a self constructed X-Y-stage allowing the precise movement of the sample. For the determination of the cells position during the irradiation, an automatic cell-recognition is needed. By testing several microscopic methods it was found that only fluorescent microscopy give reliably good results. To automate the irradiation, a software was developed that takes over the movement of the sample, the cell-recognition and the control of the microprobe. In first experiments it was shown that the aimed irradiation of cells with an accuracy of about +/-1.5µm is possible with this setup.